Method of oxidizing aluminum alkyls



Dec. 9, 1958 l. KIRSHENBAUM ET L 2,363,395

METHOD OF OXIDIZING ALUMINUM ALKYLS Filed June 12, 1956 2 Sheets-Sheet 1 F IG.I

EFFECT OF DILUENT CONCENTRATION ON OXIDATION RATE m E 2 750- I 2 Q I COMPLETE OXIDATION Q I E 500- Y O 5 l 5 Q I E 250 I m E I,

0 20 4o 60 so I00 WT SOLVENT (n-HEPTANE) Isidor Kirshenboum Stanley 8. Mirviss Theodore Lemiszka Inventors Dec. 9, 1958 l. KIRSHENBAUM ETAL 2,863,895

METHOD OF OXIDIZING ALUMINUM ALKYLS Theo ore Lemiszka By Attorney METHOD OF OXIDIZENG ALUMINUM ALKYLS Isidor Kirshenbaum, Union, Stanley B. Mirviss, Roselle, and Theodore Lerniszka, Rahway, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application June 12, 1956, Serial No. 590,863

Claims. (Cl. 260-448) This invention relates to a process of preparing aluminum alcoholates and alcohols from aluminum trialkyls. This process particularly concerns oxidizing aluminum trialkyls to form the corresponding alcoholates which may be hydrolyzed to form the corresponding alcohols. More particularly, this invention relates to an improved process of completely oxidizing aluminum trialkyls at a rapid rate.

According to this invention, an aluminum trialkyl or mixtures of aluminum trialkyls wherein each alkyl radical contains from 2-20 or more carbon atoms are oxidized under carefully controlled temperature conditions and in the presence of specific amounts of diluents to result in a rapid and complete oxidation.

The aluminum trialkyls which are amenable to the present process may be defined as having the following wherein the Rs represent the same or different alkyl radicals containing from 2-20 or more carbon atoms each. Thus typical aluminum trialkyls include aluminum trihexyl, trioctyl, tridecyl, tridodecyl, etc. The mixed aluminumtrialkyls are illustrated by the following: aluminum hexyl-dioctyl, aluminum dihexyl-octyl, aluminum butyl-octyl-dodecyl; aluminum diheptylnonyl and so forth.

The particular manner in which these aluminum trialkyls are prepared is not a critical factor of this invention; however, to illustrate the utility and versatility of the instant invention a few general methods of preparation will be briefly outlined.

Low molecular weight aluminum trialkyls which fall within the scope of the above formula may be prepared by reacting a low molecular weight alkyl halide with an aluminum metal preferably in the form of an alloy with magnesium at elevated temperatures.

T o prepare a higher molecular weight aluminum trialkyl, e. g. trioctyl, it is possible to react a higher olefin, e. g. n-octene-l, with a low molecular weight aluminum trialkyl to produce aluminum trioctyl as shown in the following equation:

If mixed aluminum trialkyls are desired as the starting material, a low molecular weight aluminum trialkyl may be reacted with a lower olefin under elevated temperatures to grow the lower olefin onto the alkyl radicals of the aluminum trialkyl. The following equation is illustrative of this so-called growth reaction:

' Time in Minutes far 25% Oxidation 2,863,895 Patented Dec. 9, 1958 ice alkyls are all straight chain or normal which would be extremely desirable for the preparation of straight chain alcoholates and/or alcohols. Generally the growth product aluminum trialkyls will be a smear of various compounds wherein the alkyl radicals will contain from 220+ carbon atoms, averaging between about 8 to 12 carbon atoms each.

In accordance with this invention it has been found that the use of an inert hydrocarbon diluent comprising aromatics such as benzene, toluene, xylene and Varsol and C -C paraffins, i. e. pentane, hexane and heptane (normal or branched chain) permits a marked increase in the oxidation rate of the aluminum trialkyl.

To illustrate the increased reaction rate obtainable, aluminum trioctyl was oxidized to the alcoholate with and without a diluent under the following conditions and with the results shown. Air was bubbled through the aluminum alkyl mixture; however, oxygen or any oxygen containing gas would be equally suitable.

TABLE I Diluent n-Heptane None Time in Minutes for 50% Oxidati0n 6 13 Time in Minutes for 100% Oxidation 90 The above tests show that the employment of a hydrocarbon diluent increases the reaction rate about tenfold, permitting complete oxidation in a relatively short period of time. The preferred conditions for oxidation include 0-100 C. and l-SO atmospheres pressure or the equivalent oxygen partial pressure for about 50-150 minutes. The diluent employed may be completely or substantially completely recovered from the oxidized aluminum alkyls, i. e. alcoholates, by simple distillation. From a practical standpoint, the use of a diluent in the oxidation stage will affect the economics of the entire operation. if less than one-tenth of the mixture to be oxidized is active aluminum alkyl, the reactor size, cooling apparatus, throughput rate and the like required would be far in excess of that required when treating 100% oxidizable aluminum alkyl to obtain the same amount of product. With regard to the diluent concentration it has been found that within a fairly critical range optimum results are obtained. It has been discovered that the employment of at least wt. percent solvent for the oxidation step results in a very marked decrease'in reaction time. While the use of less than about 80 wt. percent solvent will shown an increased reaction rate, this increase is relatively minor until about 80 wt. percent solvent or diluent is employed. On the other hand increasing the solvent concentration to over wt. percent further improves the reaction rate only slightly and the disadvantages incurred as a result of using excess diluent makes-uch use economically unattractive. In accordance with this invention the aluminum alkyl is oxidized in the presence of sufficient diluent so that the oxidation rate is a multiple of that attainable in the absence of a diluent. Preferably a preponderating proportion of diluent is employed to result in an oxidation rate of a high multiple of that attainable in the absence of diluent.

The effect of diluent concentration, as plotted against time of complete oxidation is shown in Figure 1 of the drawing. The circles represent results of oxidizing aluminum trioctyl at 30 C., p. s. i. g. with 1 liter air per minute requiring the specified times for complete oxidation. Figure 2 shows a comparison of oxidation rates employing 85 wt. percent diluent, 70 Wt. percent diluent and no diluent. Decreasing the diluent concentration from 85 to 70 wt. percent almost doubles the time required for complete oxidation.

Although, in a preferred embodiment of this invention, the aluminum alcoholates are hydrolyzed to form the alcohols, it is to be understood that the alcoholatcs may be employed for other uses such as in the production of adsorbent alumina, catalysts for chemical reactions and the like. Also, alcoholates may be reacted with organic carbonyl compounds such as ketones and aldehydes whereby the carbonyl compounds are hydrogenated to the alcohols. This reaction may be carried out in the presence of a hydrogen donor such as isopropyl alcohol.

The next step for the preparation of alcohols is to hydrolyze the aluminum a1coholate-diluent mixture to form the corresponding alcohols. However, if the diluent employed is a C,-C paramn, it should be removed prior to hydrolysis by any conventional means such as simple distillation, since these paraffins which have boiling points close to the low molecular weight alcohols, u

e. g., C2C.; alcohols, would azeotrope therewith causing separation ditficulties. If, however, pentane or hexane is employed in the oxidation step, separation dimculties would be nonexistent as far as C, and higher alcohols are concerned and these paratfins may be allowed to remain in the hydrolyzing stage. Due to the viscous nature characteristic of many aluminum alcoholates it will be desirable, although not necessary, to employ a diluent in the hydrolyzing stage. Hydrolysis may be carried out by any conventional means. In general, the aluminum alcoholate, either undiluted or diluted with about 0.5-2 volumes of low molecular weight hydrocarbon diluent, e. g. pentane or hexane, may be treated with an aqueous hydrolyzing solution which may contain HCl, H 50 HNO NH NaOH, KOl-l, water soluble organic acids, bases or the like. Alternatively, steam may be employed to hydrolyze the alcoholates. Generally, from 0.5 to 10 volumes of aqueous medium per volume of alcoholate will be employed although this amount may be varied. Temperature during hydrolysis will preferably be maintained between about 20 to 90 C. fer a period of 0.5-5 or more hours. A preferred method for hydrolyzing is to slowly add the solvent-alcoholate mixture into the aqueous hydrolyziug medium with constant agitation. It is also preferable to continue the stirring or agitation after all of the aluminum alcoholatediluent mixture has been added. After the addition of the alcoholate-diluent and the agitation is completed, the mixture is then allowed to settle until the organic phase separates. The water layer is then separated from the alcohol-diluent layer. and the diluent separated from the alcohol by straight distillation. Any alcohols remaining in the aqueous layer together with the aluminum hydroxide formed may, if desired, be extracted with a solvent such as ether to recover additional product, or the alcohols may be stripped from the aqueous layer using steam or inert gas.

Example 1 50 grams of wt. percent aluminum trioctyl in heptane diluent were placed in a reactor and air bubbled through at the rate of 1 liter of air per minute for a period of 90 minutes at 0 p. s. i. g. and 30 C. At the end of 90 minutes, the 0 content of the air emanating from the reactor was the same as the 0 content of the air being bubbled through the reaction mixture, indicating complete oxidation at thistemperature. The oxidized mixture was then distilled to remove as the distillate 90- 100% of the n-heptane employed. The aluminum alcoholate recovered from the oxidation stage is then admixed with an equal volume of hexane and hydrolyzed with an equal volume of aqueous NH, 1 cc, of concentrated NH OH per 10 cc. of distilled water) with constant stirring for a period of 10 minutes after complete addition of the alcoholatc. The aluminum alcoholatcdiluent mixture is added dropwise at a rate of 0.5-4 liters in about 0.5-1.5 hours. The aqueous mixture is then allowed to stand whereupon a top alcohol layer consist ing of n-octanoll in hexane is recovered. This mixture is then fractionated to recover n-octano] as the distillate in of the theoretical yield.

Example 2 50 grams of aluminum trioctyl were oxidized in the same manner as described in Example 1 at a temperature of C. 283 grams of n-heptane were employed as the diluent for the oxidation stage. Hydrolysis was carried out as recited in Example I with complete oxidation under these conditions requiring about 80 minutes.

Example 3 50 grams of 15 wt. percent aluminum trihexyl in n-heptane were oxidized as described in Example 1 at 30 C. 60 minutes were required for complete oxidation.

Example 4 The procedure of Example 1 was repeated using 38.5 grams aluminum trihexyl in 218 grams of n-heptane. Complete oxidation required about 50 minutes.

Example 5 The procedure of Example 1 was repeated using 73.0 grams aluminum tridodccyl in 486 grams of n-heptane. Complete oxidation required about 75 minutes.

The principal advantages of the present process may summarized as follows:

(1) A marked increase in the oxidation rate is effected by the employment of inert hydrocarbon diluents within certain concentrations.

(2) Employing the diluent within certain concentration ranges, the process is made economically attractive by a more efiicient use of reactor space. temperature control and the like.

Having thus described the invention. it is apparent that it is capable of numerous useful modifications limited only by the scope of the appended claims.

What is claimed is:

l. A process of oxidizing an aluminum trialkyl which comprises contacting a mixture comprising at least 80 wt. percent of an inert hydrocarbon solvent and an aluminum trialkyl wherein each alltyl radical contains from 2-20 carbon atoms with an oxygen containing gas for a period of time sufiicient to substantially completely oxidize said aluminum alkyl to the corresponding aluminum alcoholate.

2. A method of substantially increasing the oxidation rate of an aluminum trialltyl which comprises admixing an aluminum trialltyl wherein each alltyl radical contains from 2-20 carbon atoms with an inert hydrocarbon solvent, to form an aluminum trialkyl-solvcnt mixture containing about 80-90 wt. percent of said inert hydrocarbon solvent oxidizing the aluminum trialltyl by contacting said aluminum trialkyl-solvent mixture with an oxygen containing gas for a period of time sutlicient to substantially completely oxidize said aluminum triallzyl to the corresponding aluminum alcoholate.

3. A method in accordance with claim 2 wherein the solvent comprises C -C paratfins.

4. A method in accordance with claim 2 solvent comprises an aromatic hydrocarbon.

5. A method of preparing alcohols containing from 2-20 carbon atoms per molecule which comprises contacting an aluminum trialkyl wherein each alkyl radical contains from 2-20 carbon atoms with an oxygen conwhcrcin the taining gas in a mixture containing 80-90 wt. percent of an inert hydrocarbon diluent for a period of time suflicicnt to convert substantially all of said aluminum trialkyls to the corresponding alcoholate, hydrolyzing the resultant aluminum alcoholate by admixing therewith an aqueous hydrolyzing solution, separating and recovering a C2-C20 alcohol.

6. A method of oxidizing a mixture of aluminum alkyls having the following formula:

R1 Al-Ri R wherein each R represents an alkyl radical having 2-20 carbon atoms and wherein said alkyl radicals average between 8-12 carbon atoms each, which comprises contacting 10-20 wt. percent of said aluminum alkyl mixture in 80-90 wt. percent of an inert hydrocarbon solvent with an oxygen containing gas at -100 C. and 1-50 atmospheres pressure for 50-150 minutes whereby substantially all of the aluminum alkyls are oxidized to the corresponding alcoholates.

7. A method in accordance with claim 6 wherein the solvent comprises a C -C paraflin.

8. A method in accordance with claim 6 wherein the solvent comprises an aromatic hydrocarbon.

9. A method in accordance with claim 6 wherein the aluminum alcoholates are subsequently hydrolyzed with an aqueous medium at 20-90 C. for a period of at least 0.5 hour.

10. A method in accordance with claim 6 wherein the air is bubbled through the aluminum alkyl mixture at the rate of 1 liter of air per minute per grams of aluminum alkyl.

References Cited in the file of this patent UNITED STATES PATENTS 2,163,720 Vaughn June 27, 1939 2,318,033 Van de Griendt et al May 4, 1943 2,579,251 Coates et al Dec. 18, 1951 2,666,076 Rex et al. Jan. 12, 1954 2,687,423 Mesirow Aug. 24, 1954 OTHER REFERENCES Uses and Applications of Chemicals and Related Materials, Gregory, Reinhold Publishing Corp, 1939.

Ziegler et al.: Angewandte Chem. vol. 67, 1955, No. 16, pp. 424 to 426. 

1. A PROCESS OF OXIDIZING AN ALUMINUM TRIALKYL WHICH COMPRISES CONTACTING A MIXTURE COMPRISING AT LEAST 80 WT. PERCENT OF AN INERT HYDROCARBON SOLVENT AND AN ALUMINIM TRIALKYL WHEREIN EACH ALKYL RADICAL CONTAINS FROM 2-20 CARBON ATOMS WITH AN OXYGEN CONTAINING GAS FOR A PERIOD OF TIME SUFFICIENT TO SUBSTANTIALLY COMPLETELY OXIDIZE SAID ALIMINUM ALKYL TO THE CORRESPONDING ALUMINUM ALCOHOLATE. 